UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of report (Date of earliest event reported): September 10, 2013

METLIFE, INC.

(Exact Name of Registrant as Specified in Its Charter)

212-578-2211

(Registrant’s Telephone Number, Including Area Code)

N/A

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Item 3.03. Material Modification to Rights of Security Holders.

On September 10, 2013, MetLife, Inc. (the “Company”) remarketed $999,886,000 in aggregate principal amount of its 4.368% Series D Senior Debentures (the “Series D Debentures”). Effective September 11, 2013, the stated maturity of the Series D Debentures will be September 15, 2023. The Series D Debentures were originally issued in November 2010 as $1.0 billion aggregate principal amount of Series D Senior Debentures due 2024 pursuant to an Indenture dated as of November 9, 2001 between the Company and The Bank of New York Mellon Trust Company (as successor in interest to J.P. Morgan Trust Company, National Association (as successor in interest to Bank One Trust Company, N.A.)), as Trustee (the “Trustee”), as supplemented by the Twenty-First Supplemental Indenture, dated as of November 1, 2010 between the Company and the Trustee, and have terms described in the Company’s Prospectus Supplement relating to the remarketing thereof dated September 3, 2013 (the “Prospectus Supplement”). The Series D Debentures initially constituted part of the Company’s common equity units issued in November 2010 (the “Common Equity Units”).

In addition, on September 10, 2013, Series D Debentures of $114,000 aggregate principal amount were delivered to holders of the Common Equity Units who elected cash settlement of the related Series D stock purchase contracts.

The Series D Debentures were offered and sold pursuant to the shelf registration statement on Form S-3 (File No. 333-170876), filed with the U.S. Securities and Exchange Commission on November 30, 2010, and the Prospectus Supplement.

A form of the security certificate representing the Series D Debentures is attached hereto as Exhibit 4.1 and is incorporated herein by reference.

Item 8.01. Other Events.

A copy of the opinion letter of Willkie Farr & Gallagher LLP relating to the validity of the remarketed Series D Debentures is filed as Exhibit 5.1 hereto.

- 2 -

Item 9.01. Financial Statements and Exhibits.

- 3 -

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: September 10, 2013

- 4 -

EXHIBIT INDEX

- 5 -